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EP: Fachverband Extraterrestrische Physik

EP 10: Poster

EP 10.15: Poster

Wednesday, March 28, 2007, 18:00–20:00, H46

Suprathermal tails of solar wind ion velocity distribution functions from ACE/SWICS — •Lars Berger¹, Muharrem Köten¹, Jim Raines², Robert F. Wimmer-Schweingruber¹, and Thomas H. Zurbuchen² — ¹Institut für Experimentelle und Angewandte Physik, University of Kiel, D-24098 Kiel, Germany — ²University of Michigan, Atmospheric, Oceanic, and Space Sciences 2455 Hayward St., Ann Arbor, MI 48109, USA

Solar wind ion velocity distributions (VDFs) are shaped by two processes in the inner heliosphere. Investigation of VDFs allows us to distinguish the relative importance of Coulomb-interaction which tends to drive the solar wind isothermal and wave-particle interactions which tend to heat the wind in a mass-proportional manner. We analyse data from the solar wind ion composition spectrometer (SWICS) on the Advanced Composition Explorer (ACE) using a maximum-likelihood analysis technique based on Poissonian statistics that is well adapted to the low fluxes of the suprathermal tails on the flanks of velocity distributions. We present results for different extended periods of constant solar wind speed, and compare them to previous studies.